Method of centrifugally casting pipe



Patented Oct. 22, 1935 METHOD or cmrrmruqmr I oas'rmc. rm:

Frederickfi. Langenberg, Edgewater Park, and Horace 8. Hunt, Burlington,N. J., assignors to United States Pipe and Foundry Company, Burlington,N. 3., a corporation of New Jersey No Drawing. Application December 24,1934,

I Serial No. 758,938 a Our invention relates to the method ofcentrifugally casting cast iron pipe described in the patent to Russelland Langenberg, Number 1,949,433, granted March 6; 1934, and, moreparticularly, to the utilization of this method in the production ofpipe having the characteristic structure which forms the subject matterof the Russell and Langenberg patent, Number 1,954,892,

' granted April 17, 1934. Generally speaking, the

method is characterized in that an externally cooled metalliccentrifugal pipe mold is progressively coated with finely divided drycoating material by directing a jet of carrier gas charged with suchfinely divided dry coating material against successive areas of the moldsurface and then, the mold being in rotation, pouring molten metal incontact with the so coated portions of the mold so as to bring about theformation of a centrifugally lcast pipeand preferably the coat-- ing isapplied to the mold progressively along its length and the molten metalprogressively poured along the length of the mold immediately followingthe deposit of the coating upon the sections of the mold with which thestream of molten metal comes in contact, as is described in the saidRussell and Langenberg patents. As is pointed out in the Russell andLangenberg patents, theprocess gives its best results wherethe'thicknessof the coating applied to the mold does not substantially exceed suchthickness as will bring about the formation of the pipe casting withoutchill and this is particularly important where a pipe is to be casthaving the structural features described in, the Russell andLangenbergpatent,

In thepractice of the Russell and Langenberg process, it hasbeen foundthat defective pipes are occasionally produced which are unfit fordelivery and use and have to be scrapped and v which the carrier gas ischarged, of an unduly high percentage of comparatively large sizeparticles of the material making up the bulk of the coating and thesecond of which is the occurrence in the material with which the carriergas jet is charged of an unduly large percentage of veryflnely dividedparticles. It will be understood that with the grinding of such materialfor coating to bring it to the necessary fine state of division therewill be produced a ground material made up of particles of differentsizes and that, for commercial reasons, it is quite impracticable 'tograde the particle size of the ground product so as to eliminate theoccurrence of particles of relatively very different sizes but havingsatisfied ourselves that the presence in the ground material" charged tothe carrier gas jet of relatively large and very small particles was notincompatible with the production of an entirely l5 satisfactory coatingby the Russell andLangenberg method provided that the relatively largeand very fine particles did not occur in the carrier gas charge inunduly large proportions, we

proceeded by experimentation to ascertain approximately conditions as toparticle-size of the finely divided dry coating material charged to thecarrier gas jet which would give the best results as applied in the formof a coating to the mold surface and we have ascertained that bycharging the carrier gas jet with finely divided dry coating material ofsuch size that not more than 5% of the particles will be retained on asieve of 150 mesh while not less than 10% of the particles willberetained on a sieve of 200 mesh, that a very materially better coatingcan be applied to theface of the mold than would be the case either ifmore than 5% of the particles were retained on the 150 mesh screen orless than 10% would be'retained on a 200 mesh screen. Again, we havefound it desirable, although not absolutely necessary, that at leastsome percentage of the finely divided coating material should beretained on the 150 mesh screen and we have also found it highlydesirable that not less than 40 15% of the particles should be retainedon a 200 mesh screen.

While we believe that with all finely divided dry coating materialswhich may be employed to'" charge the carrier gas jet and form the moldcoating, the grinding of the material to the state of particle divisionwhich willlnjsure that not more than 5% of the particles will beretained on a 150 mesh screen and not lessthan l0to 15% re-- tained on a200 mesh screen will give materially better results in the formation ofan effective coating for the mold of the Russell and Langenberg process,we believe that the improved reg-' 'ulationof the particle size .isespecially advantageous where ferro-silicon is used as the coatl6particles will be retained on a 200 mesh screen that it is practicableby the Russell and Langenberg process to build up upon the mold a verythin coatingwhich is entirely eflective to prevent chill in the castingand to bring about the formation of the advantageous structure describedin the Russell and Langenberg patent, 1,954,892, while, at the sametime, the coating is materially less liable to slip on the mold eitherduring application or the subsequent casting and, again, if the'ferro-silicon embodies an undue proportion of exceedingly fineparticles, such as those of micron size, it has been found that when airis used as the carrier gas the jet is liable to ignite in which case noefficient coating is deposited upon the mold and the deposit of thefinely divided oxides upon the mold is very liable to bring aboutdistortions in the mold shape involving at least'a temperorary dis-useof the mold in the casting of pipes. In using ferro-silicon as a coatingmaterial in the Russell and -Langenberg process we'have successfullyused alloys containing from 40 to 95% of silicon, but believe that thebest results are secured where the alloy has a silicon content ofapproximately 75%, say, between 70% and 80%, and finely divided dryparticles of ferro-silicon containing this proportion of-silicon havebeen found to give notably good results when so round as to comply withthe conditions as to particle size which we have above described.

It will be understood that the conditions of the finely divided drycoating material as to particle size are to be ascertained by testingsamples of the ground material in laboratory sieves and under conditionsas to the cleanness of the 'slevev and the observance of the propertechnique which are ordinarily observed in sieving tests made inlaboratories.

It will be understood from what we have said that our invention consistsin the practice of the Russell and Langenberg process by charging thecarrier gas jet witha finely divided dry coating material of suchmake-up with regard to its particle size that not more than 5% of itsparticles will be retained on a mesh screen and not less than 10% andpreferably not less than 15% of its particles will be retained on a 200mesh screen and that particularly our invention has reference tothe-charging of the carrier gaswith ferro-silicon ground to suchparticle size as will comply with these requirements.

It has been found advantageous, as is pointed out in the application ofStuart, Hunt and Arnold, filed March 22, 1934, Serial Number 716,- 768,to charge the carrier gas Jet with finely divided dry coating materialwith which isadmixed a percentage of s lica sand or equivalent moldsurface, and it must be understood that in specifying and claiming thecharging of the consists in'charging the jet of carrier gas with acarrier gas Jet with finely divided dry coating material made up ofparticles not more than 5% of which will be retained on a 150 meshscreen and not less than 10 to 15% of which will be retained on a 200mesh screen we are not to be 5 understood as excluding from admixturewith the so described finely divided dry coating material a percentageof the relatively large sand grains or as having in view the presence,of such sand grains in providing that not more than 5% of the finelydivided dry coating material should be retained on a 150 mesh screensince substantially all of the sand grains would be retained on such ascreen and as used would materially exceed 5% (of the mixture of finelydivided mold is coating material and relatively large grains of sand.

Having now described our invention, what we claim as new and desire tosecure by Letters Patcut, is:

1. In the method of centrifugally casting pipes in which an externallycooled centrifugal metallic pipe mold is coated with a finely divideddry coating material by progressively directing against adjacentsections of the mold surface a jet of a carrier gas charged with finelydivided dry particles of mold coating material and the mold being inrotation at a speed effective for the centrifugal casting of pipe,pouring molten metal in contact with so coated portions of the mold toform a centrifugally cast pipe, the-improvement which consists incharging the jet of carrier gas with'a finely divided dry coatingmaterial of such a state of division that not more than 5% of itsconstituent particles will be retained on a 150 mesh screen and not lessthan 10% of its constituent particles will be retained on a 200 meshscreen. a

2. In the method of centrifugally casting pipes in which an externallycooled centrifugal metallic pipe mold is coated with a finely divideddry coat ing material by progressively directing against adjacentsections of the mold surface a jet of a carrier gas charged with finelydivided dry particles of mold coating material and the mold being i inrotation at a speed effective for the centrifugal I casting of pipe,pouring molten metal in contact with so coated portions of the mold toform a centrifugally cast pipe, the improvement which finely divided drycoating material of such a state of division that some but not more than5% of its constituent particles will be retained on a 150 mesh screenand not less than 10% of its constituent particles will be retained on a200 meshscreen.

3. The method of centrifugally casting pipe as set forth in claim' 1, inwhich the particle size of the finely divided dry coating material withwhich 60 the carrier gas jet is charged is such that not less than 15%of its particles will be retained on a 200 'mesh screen.

in rotation at a speed eil'ective'for the centrifugal casting of pipe,pouring molten metal in contact with 'so coated portions of the mold toform a centrifugally cast pipe, the improvement which consists incharging the jet of carrier gas with 7;

s,ois,oas

divided drypai'ticles oi term-silicon of such psr- J finely divided dryparticles or ierro-silioon of such particle size that not more than ofthe par ticles will be retained on a 150 mesh screen while not less thano! the particles ll heretsined on a. 200 mesh screen.

5. In the methodof 'oentrifu ally cestin: P 9 in which an externallycooled oentriiugal metallic pipe mold is coated with a finely divideddry coatin: material by progressively directing elninst adjacentsections of the mold surface s jet of a carrier gas charged with timelydivided dry particles of mold coating material and the mold heinl inrotation at a speed eilective tor the centrimlel casting of pip pouringmolten metal in contact with so coated portions of the mold to term acentriiugally cast pipe, the improvement whichconsistsinchorzingtheietoicarriermwithiinely of silicon.

ticle size that some but not more than 5% o! the particles will beretained on a 150 mesh screen while not less than 10% o; the particleswill be retained on a 200 mesh screen.

6.- The method of oentrimzally casting pipe as set forth in claim 4, inwhich the particle-size oi! the finely divided dry term-silicon is suchthat not less than loq, o! the particles will be retained on a 200 meshscreen.

7. 'lhe method of oentriiugally casting pipe as set iorthin claim 4, inwhich theterro-silicon is or a composition comprising between and HORACE8. HUNT.

msnamcx c. mnbmnna. is

